In automated fabrication plants or inside a complex wafer-processing tool, work pieces travel from one process station to another. At these process stations various operations are performed on the work pieces. Some process stations perform operations on the work pieces for a longer period of time than other process station. Also, some process stations are able to operate on a larger number of work pieces than other process stations. Additionally, the time taken to transfer the work pieces between process stations is an important fabrication parameter. One difficulty in monitoring the progress of work pieces in fabrication plants is that information involving plant processes is not provided in a manner that allows an operator to quickly visualize plant or tool parameters in an easy to use and efficient manner. Also, there are no simple ways to use simulated data, either generated by a simulation machine or generated using knowledge of plant parameters, to produce a visual representation of a processing process for planning purposes.
To overcome this problem, different process visualization schemes have been proposed. One scheme is disclosed in U.S. Pat. No. 6,099,598 issued to Yokoyama on Aug. 8, 2000. This invention discloses a method of displaying a semiconductor manufacturing process. The display shows the transportation of a semiconductor wafer and the processing of the semiconductor wafer on a horizontal line. Additional wafers are illustrated on other horizontal lines, one line on top of another. This approach, however, makes it difficult to see what process station the wafer is in. Additionally, it does not give an indication of the quantity of wafers in a process station.
Another scheme is detailed in U.S. Pat. No. 6,230,068 and issued to Wu et al on May 8, 2001. This patent discloses the collection of data from different stages of a process line. The data from each stage is placed on a bar chart. The bar charts are arranged in pairs representing process steps. However, these charts do not indicate what process station a work piece is in, do not indicate when work pieces are transferred and do not indicate the quantity of work pieces at each process station at a given time.
In view of the problem, described above, the need remains for a graphical representation of a processing process that provides a simple way to determine plant parameters.